1. Technical Field
The present invention relates to a method to control the bulk density of packaged fried snack pieces. More specifically, this invention relates to imparting a random shape or curvature to each snack piece during cooking or frying in such a way as to control the resultant bulk density of such product when packaged.
2. Description of Related Art
Random Frying
In the food industry, there are two typical methods of frying snack pieces such as potato chips: random frying and constrained frying. One popular random frying method is to fry uncooked pre-formed snack pieces in a random frying section of a multi-layer continuous fryer and allow buoyancy forces to impart a random shape or curvature to each snack piece. Several patents illustrate such random frying methods, as those disclosed in Pringle et al., U.S. Pat. No. 2,286,644 entitled “Method and Apparatus for Processing Potatoes” issued Jun. 16, 1942, and Anderson et al., U.S. Pat. No. 3,149,978 entitled “Process for Cooking Corn Dough in the Form of Chips” issued Sep. 22, 1964 and assigned to Arthur D. Little, Inc.
U.S. Pat. No. 3,608,474 issued Sep. 28, 1971 to Liepa, discloses a random frying method for making potato chip products. Liepa '474 suggests slicing raw potatoes, cooking these loose slices in a reservoir of hot oil for a predetermined time where the slices are fried to a crisp state, and then removing the fried chips from the oil. The chips so prepared have a random surface curvature which is influenced by the diameter and thickness of the potato slices and is dependent both upon the amount of time the slices are immersed in the hot oil and the temperature of the oil. In the prior art, a constrained or form frying method is difficult to use with snack pieces of different sizes or shapes. Instead, random frying is typically used on these pieces of varying size or shape.
Liepa '474 also teaches that the random shapes which the chips assume require that they be randomly packaged. Random packing is used because it is relatively cheap, requires less energy and is less complicated than packing snack pieces into a high-density nested arrangement or packed alignment. Randomly packed snack piece packages require larger amounts of store shelf and consumer pantry shelf space. Generally, when a consumer opens such package, the snack pieces have settled and the bulk density has increased leaving a substantial void within the package. It would be ideal if the randomly packed pieces filled the entire package at the time the package is opened even after some settling occurred during shipping and handling.
According to the prior art, and with reference to FIG. 1, uncooked chip pre-forms 120 are continuously fed by an entrance conveyor 110 into cooking oil 104 of a random frying section 106 of a continuous fryer 102. In a continuous fryer 102, cooking oil 104 generally flows from an entrance conveyor 110 toward an exit conveyor 114 carrying chip pre-forms 122 with it. As relatively moist chip pre-forms 122 are first introduced into cooking oil 104, their weight 122 is usually greater than the buoyancy forces acting on them and the moist chip pre-forms 122 remain submersed in the oil without aid. As chip pre-forms 122 continue to cook and move along the path inside the continuous fryer 102 (from left to right in FIG. 1), moisture escapes from the chip pre-forms 122 and the buoyancy forces become greater than the weight of the chip pre-forms 122. At that point, the chip pre-forms 124 generally float near the surface of the oil as they approach a prior art submerger 112. At this point, chip pre-forms 124 are generally, not rubbery, and do not have a tendency to stick to each other.
A prior art submerger 112 generally turns at a speed slower than the flow of cooking oil 104. A prior art submerger 112 usually has one or more optional and generally straight paddles, cleats or fins 116. These fins 116 help gather the roughly monolayer of floating chip pre-forms 124 into a multi-layer of submerged chip pre-forms 126. The fins 116 also help ensure that submerged chip pre-forms 126 do not clump or stick together. By submerging the cooking chip pre-forms 126, the pre-forms 126 are more evenly cooked on both sides. Cooked chips 128 leave the prior art submerger 112 and exit the continuous fryer 102 on an endless exiting conveyor 114.
According to the prior art, reference to FIG. 1a, the majority of submerged chip pre-forms 132 lay flat as they are transported along the cooking path. These pre-forms 132 leave the continuous fryer as generally flat cooked chips; any curvature in the cooked chips 128 is the result of random cooking forces acting on a submerged chip pre-form 132. However, by chance a few submerged chip pre-forms 134 overlap or randomly press against a fin 116 or another submerged chip pre-forms 132 in such a way as to gain an exaggerated curvature. FIG. 6 illustrates typical resulting shapes of triangular snack pieces cooked according to the prior art. The snack pieces 128 are generally flat, but some have a minimal curvature. More or less curvature can be obtained by using the method of constrained frying.
Constrained Frying
The other typical method of frying snack pieces is through the use of constrained or form frying. Several patents disclose methods of imparting a curvature to chip-type products made from a dough sheet by constrained frying methods. For example, a method to produce rippled chip-type products is disclosed in U.S. Pat. No. 2,286,644 by Pringle et al., issued Jun. 16, 1942 entitled “Method and Apparatus for Processing Potatoes.” Other U.S. patents disclose other similar methods to impart a desired final curvature or shape to a snack piece. In U.S. Pat. No. 3,998,975 issued Dec. 21, 1976, Liepa et al. discloses a method to form uncooked snack pieces into a desired shape by drying the pieces sufficiently and frying the pieces to a finished state before packaging.
In U.S. Pat. No. 3,576,647 issued Apr. 27, 1971, Liepa discloses a constrained frying method wherein mold halves each provide multiple openings distributed over the mold surfaces to permit the frying oil to pass through and come into contact with the constrained food product. The mold halves cooperate to hold the dough sections and restrain them during the frying so that the fried products conform in surface curvature with that of the mold surfaces. Similarly, in related U.S. Pat. No. 3,608,474 issued Sep. 28, 1971, and U.S. Pat. No. 3,626,466 issued Dec. 7, 1971, Liepa discloses the same molds and passes them through frying oil and form-fries dough pre-forms into crisp chips thereby imparting a uniform size and shape to each chip.
U.S. Pat. No. 3,520,248, issued Jul. 14, 1970 to MacKendrick, discloses a machine to continuously and uniformly cut and cook snack pieces or chips from a sheet of dough. MacKendrick discloses a machine to positively convey snack pieces through the frying medium in the same controlled manner as disclosed by Liepa '474 where the resulting chips have a uniform color, texture, and shape. The MacKendrick invention improves the Liepa '474 machine by using a reciprocating cutter in place of a rotary cutter which can be operated at significantly higher speeds.
U.S. Pat. No. 3,149,978 entitled “Process for Cooking Corn Dough in the Form of Chips” granted on Sep. 22, 1964 to Anderson et al., teaches a method of imparting a controlled bent configuration to a corn masa dough chip which is cooked by deep-fat frying. Further, this invention teaches an apparatus for inducing a desired shape to the corn chips during cooking. The desired configuration is done through the use of a series of parallel wires which are mounted on a frame such that the wires may be controllably moved within the oil. The spacing of the wires is adjusted so that it is somewhat less than the diameter or maximum dimension of the chip which is to be cooked. The wires may be periodically immersed into the cooking oil to strike a portion of the cooking chips and then withdrawn. When forcing the parallel wires into the cooking oil, the wires impart a curvature to the chips either when the wires strike the chips, pushing them deeper into the oil, or when the chips rise after being pushed momentarily deeper into the cooking oil, or by a combination of these actions. By this process not all of the chips are contacted and bent. Anderson et al. '978 teaches that it is preferred not to give a bend to all of the chips because it is desirable to package corn chips which are a combination of those having a flat and bent configuration, the latter amount consisting of about 25% to 75% of the total number of chips.
In a recent U.S. patent application, Dove, et al. discloses a single mold fryer. A single layer of cooking chips are given a uniform shape as chips are disposed against a curved or contoured submerged conveyor surface or mold surface by buoyancy forces. The Dove patent application has the same assignee as the present application and is entitled “Single Mold Form Fryer with Enhanced Product” having a filing date of Jan. 21, 2003 and Ser. No. 10/347,993. Such form frying imparts a relatively predictable and uniform shape to each snack piece, not a random curvature.
Anderson et al. '978 mentioned above teaches that curvature must be imparted during frying before a critical time when the frying chips assume their permanent configuration or shape. This critical time occurs when a given dough formulation reaches a glass transition point. FIG. 2 illustrates the various states of a generic polymer-like substance such as dough. Referring to FIG. 2, polymer substances and farinaceous dough formulations can be pliable 202, rubbery 204 or glassy 208 at a given temperature depending on the composition of the substance. The state of a dough is especially dependent on moisture concentration. In a typical case, the state of an edible chip product made of a given dough formulation, as it loses moisture while cooking at a constant given temperature, moves from a pliable rubbery state 204 through a glass transition state 206 into a permanent glassy state 208. As the chip is cooled and subsequently packaged, the chip remains in a glassy state 208. It is at the glass transition state 206 where a cooking chip pre-form loses its pliability and assumes its final shape. The glass transition state 206 is somewhat of a misnomer since the term “transition” implies an equilibrium phenomenon that is invariant to the speed of the heating, cooling or other conditions. The actual transition point for a given product formulation may depend on the speed at which a substance is heated, cooled, or dehydrated (cooked).
Packaging
Cooked snack products are generally packaged in a random fashion in a bag or other similar container. Such random packing leads to a packaged product with a certain, relatively low bulk-density. Packages with low bulk density are essentially packages wherein the volume capacity of the package is much greater than the absolute volume of the snacks contained inside. The package could contain a much higher net weight of snack pieces than the volume capacity of the package if the pieces were not randomly packaged. This inefficiency is especially evident when chips have settled during shipping.
Curved snack pieces generally have a lower bulk density when randomly packed as compared to generally flat snack pieces when randomly packed. Curved snack pieces tend not to seat against one another and tend to leave relatively larger voids between pieces as compared to flat snack pieces. In U.S. Pat. No. 4,844,919, issued on Jul. 4, 1989, Szwerc teaches that the use of curved pieces lowers packed product bulk density. Szwerc '919 teaches that the snack piece's thickness, curvature, weight and orientation must be considered and potentially optimized to achieve densities above those obtained by randomly packing such pieces. Szwerc '919 teaches the production of curved snack chips by baking. In U.S. published patent application Ser. No. 09/851,040 entitled “Snack Piece Having Increased Packed Density,” Zimmerman et al. teaches that the shape and thickness of snack pieces can contribute to lower packed densities. Zimmerman teaches that the interference between adjacent snack pieces due to irregular sizing leads to increased space between nested pieces, subsequently leading to a lower bulk density.
However, the prior art does not teach methods which would provide sufficient control of the snack piece's thickness, curvature, weight, orientation, or shape to achieve a desired bulk density. Currently, the food industry does not design a product to have desired bulk density. The food industry conforms the size of a product package to a desired weight of randomly-packed product. The package is sufficiently large to accommodate variations in bulk density. Consequently, a need exists for a method to permanently impart a particular shape to snack pieces in such a way as to produce a snack product that will have a desired bulk density when randomly packaged. Further, a need exists for producing such a snack product without lowering the productivity or throughput of the process.
Further, a need exists for a method to control the amount of change in bulk density during the time a snack product package is exposed to settling forces during shipping and handling. Specifically, a need exists to prevent settling of chips wherein a substantial void remains in the product package. A need exists for an optimal packing that would also minimize breakage of chips. The benefit of filling this need would be an improved perception by consumers that the package is more substantially filled with product. Further, there is a need for loosely packed consumer products. In such a case there would be a lower bulk density and less shingling of chips within each package.
Further, a need exists for a method and apparatus which cooks snack pieces with a more consistent, controlled, and predictable cooking time. Such method and apparatus would produce chips with a more uniform color and texture. Such a method and apparatus would meet these criteria and could be used in a high-speed production environment. It is therefore an object of this invention to provide a method of imparting a controlled bent configuration to fried snack product pieces. These and other objects will become apparent in the following detailed description.